Neurobiology of the structure of personality: Dopamine, facilitation of incentive motivation, and extraversion

Department of Psychology, University of Oregon, Eugene, OR 97403
pcollins@oregon.uoregon.edu

Published online: 01 June 1999

Abstract

Extraversion has two central characteristics: (1)
interpersonal engagement, which consists of affiliation
(enjoying and valuing close interpersonal bonds, being warm and
affectionate) and agency (being socially dominant, enjoying leadership
roles, being assertive, being exhibitionistic, and having a sense of
potency in accomplishing goals) and (2) impulsivity, which
emerges from the interaction of extraversion and a second, independent
trait (constraint). Agency is a more general motivational disposition
that includes dominance, ambition, mastery, efficacy, and achievement.
Positive affect (a combination of positive feelings and motivation) is
closely associated with extraversion. Extraversion is accordingly
based on positive incentive motivation.

Parallels between extraversion (particularly its agency component)
and a mammalian behavioral approach system based on positive incentive
motivation implicate a neuroanatomical network and modulatory
neurotransmitters in the processing of incentive motivation. A
corticolimbic-striatal-thalamic network (1) integrates the salient
incentive context in the medial orbital cortex, amygdala, and
hippocampus; (2) encodes the intensity of incentive stimuli in a
motive circuit composed of the nucleus accumbens, ventral pallidum,
and ventral tegmental area dopamine projection system; and (3) creates
an incentive motivational state that can be transmitted to the motor
system.

Individual differences in the functioning of this network arise
from functional variation in the ventral tegmental area dopamine
projections, which are directly involved in coding the intensity of
incentive motivation. The animal evidence suggests that there are
three neurodevelopmental sources of individual differences in
dopamine: genetic, “experience-expectant,” and
“experience-dependent.” Individual differences in
dopamine promote variation in the heterosynaptic plasticity that
enhances the connection between incentive context and incentive
motivation and behavior.

Our psychobiological threshold model explains the effects of
individual differences in dopamine transmission on behavior, and
their relation to personality traits is discussed.